Almost all ammunition for hand guns consist of a casing with an ignition and drive charge and a projectile.
Brass has proved to be an excellent material for ammunition casings for small calibre hand guns and up to large calibre cannons, except for the weight. Brass has a density in the range of 8.4 to 8.7 g/cm3, such that the casings are relatively heavy and contribute strongly to limit the amount of ammunition soldiers/combat units are able to carry in the field. Another issue is that brass contains copper, which is a toxic metal, such that from an environmental point of view, it is a desire to replace brass casings with casings made from a different and more environmentally compatible material. In addition, another relatively recent problem is that the global copper reserves are beginning to get depleted, such that, in a public perspective, it is desired to reserve the remaining copper reserves for other more important purposes.
Consequently, alternative materials for ammunition casings for hand guns have been searched for. One material which for a long time has been tried, known to be used for the first time in the early nineteenth century, is aluminium. Aluminium may be alloyed to obtain almost the same mechanical properties as brass casings; however, it possesses only about ⅓ of the density of brass. Thus, a weight saving of about 60% for ammunition is obtainable by substituting the brass casing for an aluminium casing.
However, two problems have hampered the use of aluminium. One is that the oxide layer formed at the surface is brittle and very hard, and it tends to crack and fall off during firing of the ammunition, and form an effective abrasive agent (particles of Al2O3) in the chamber which leads to abrasive wear problems. The other problem is that aluminium has a heat resistance which is too poor to withstand the generation of heat during firing, such that a risk of the gun powder gas burning through the casing arises.